In 2007 new Guidance was introduced for use of enforcement camera to ensure their effectiveness
Safety Camera Guidance pdf

Camera Enforcement of speed limits is usually carried out as a partnership between a Local Authority that installs a speed limit and the Local Police who enforce it.

Before enforcement begins an Officer should check
Speed Limits are appropriate ( See DfT 2006 Guidance for setting Local Speed Limits)
Signage is appropriate ( See DfT Traffic Signs Manual mainly chapter 3)
Appropriate Traffic Orders are in place (See Road Traffic Acts and Procedures Regulations)

Example partnerships :- 
http://www.saferroads.org/
(Bracknell, Reading, Slough, West Berkshire, Windsor and Maidenhead, Wokingham)
http://www.sussexsaferroads.gov.uk/
http://www.staffssaferroads.co.uk/